Reference is made to FIG. 1, a light source is formed by a plurality of LED rows 010′ in parallel connection with each other in a conventional thin display device, in which the respective LED rows 010′ include at least one LED 001′ and an adjusting device 002′. In order to make the thin display device to have uniform brightness on the screen, the conventional adjusting method usually adjusts the currents of the respective LED rows 010′ to be the same. The adjusting device 002′ adjusts an impedance value to make the respective LED rows 010′ to be the same, for achieving the state of current balance.
However, in such adjusting method, the adjusting device 002′ in series connection with the respective LED row 010′ consumes more power, and the total efficiency of the light source 100′ is relatively affected, too. Moreover, the impedance value adjusted by the adjusting device 002′ is the default set in the production, and the default is different to be adjusted after assembling. The change of the impedance value depends on the influence of external factors, such as temperature and humidity thereby affecting the current balance of the respective LED rows 010′.
In addition, in order to match a rapid change of an image for the thin display device, the light source blinks and turns off transiently in a frequency of persistence of vision of human eyes, for preventing image-sticking phenomenon on the screen. The respective LED rows 010′ in the conventional light source 100′ are directly connected with the power supply 200′. An output capacitance usually exists in the power supply 200′. After the power is cut off, the power is continuously provided until the output capacitance finishes discharging. It results that the light source 100′ fades away to decrease luminance gradually when the light source 100′ is turned off. Consequently, light source 100′ causes image-sticking phenomenon on the screen.
Moreover, the respective LED rows comprise a plurality of LEDs 001′ in series connection. If any LED 001′ of the LED row 010′ is broken to form an open circuit, such LED row 010′ cannot work.